I've added an extra / mountpoint in /etc/fstab in order to be able to
access C: without /cygdrive like this:
none /cygdrive cygdrive binary,posix=0,user 0 0
none / cygdrive binary,posix=0,user 0 0
It seems to work, I can access the C: drive with just /c.
But normally an "ls /cygdrive" should list the drives, whereas "ls /"
lists the contents of the Cygwin root. So it seems there are now two
root mountpoints overlaying each other.
So I was wondering if my approach is if this is technically undefined
behavior and might conceivably break something or is it OK (less the
drive listing limitation mentioned above).
Thanks,
Rustam

The way that I do it (and have for a long time) is a line in my
.bash_profile file:

mount --change-cygdrive-prefix /
then ls /c does what you want
but ls / may not
HTH